Techniques on which the inventors of the present invention have studied include the following techniques for detecting location information of vehicles.
For example, in the railroad transportation field, it is desired to develop a new railroad system to save labor and equipment cost. An indispensable thing to realize that is a sensor technology for each railroad vehicle to recognize its location and speed highly precisely while running. Conceivable methods to detect location of each railroad vehicle include a method of detecting by a ground system and a method of detecting by a railroad vehicle system. In the current system, location detection is generally done by ground systems. Since the method using a ground system requires equipment cost and maintenance cost a lot, it has been desired to have a system for detecting locations on the railroad vehicle side.